This invention relates to documents.
Documents such as bank-notes, securities, identity cards, credentials, tickets and the like have become an indispensable aid to everyday life. The monetary or legal value of such documents is often considerable, which induces the criminal elements of society to forge, change or copy such documents.
In the industrialized countries, machines are increasingly being used to check the genuineness or identity of documents. Examples of such machines are bank-note checking and changing machines and devices for accepting travel or admission tickets. If the genuineness or identity features of documents to be checked by machine are too simple, this again forms a strong inducement to fraudulent action.
One of the safest known methods to prevent a document from being forged is to store the information indicating genuineness thereon in the form of diffraction gratings or holograms. Such diffraction gratings and holograms can be read and checked for their genuineness relatively easily by a machine. However, their production requires the use of rare, costly technical aids and considerable expert knowledge, so that any forgeries thereof which could possibly be successful can only result from large expenditure.
For the mass production of holograms, it is known to emboss them in a thermoplastic material support by means of an embossing die. The use of this duplication method has already been proposed for producing card-type means of payment, wherein holograms or diffraction gratings are embossed in a plastic support member.
Furthermore, an identity card is known which is protected against forgery by stamping a refracting pattern into a plastic support member.
However, it has not hitherto proved possible to use the hologram or diffraction grating duplication method by embossing with support members made from paper, cardboard or like materials.
The problem of the invention is therefore to provide a document of the type indicated hereinbefore which can be produced by using the known embossing method, although its support member is made from a material which, due to its fibrous, granular or cellular structure or due to its thermal characteristics is unsuitable for the application of the embossing method per se.
According to the present invention there is provided a document comprising a flat support member of non-thermoplastic material at least partly coated with a thermoplastic coating in which are embossed optical markings with a light-modifying relief structure, representing information indicating the genuineness of the document.